If it's a new minifigure parted out directly from a set, I make sure it's never assembled. I'll use a stock photo of the minifig from lego's site, or take a photo of a copy in my personal collection, and clearly note that the figure they're buying is not the instance pictured, but a brand new one, handled only through extracting from the original set and bagging for shipping, but no more than that. I'll usually use a smaller baggy for the accessories, placed inside the baggy with the minifig parts.
Once a brick has locked in with another brick using friction, it can be considered a used product in my opinion.